#0, Cut Triangle in Half
Posted by Bractals on Jul-08-03 at 07:16 AM
Hi, I came up with the following construction for the given problem. It checks out with Sketchpad. See what you think. Bractals PROBLEM: Given an arbitrary point and triangle. Construct a line through the point that divides the triangle into two polygons of equal area. NOTATION: ^ denotes set intersection. Let X' denote the midpoint of the side of the triangle opposite the vertex X. If X and Y are distinct points, let L(XY) denote the line determined by points X and Y, R(XY) denote the ray starting at point X and passing through point Y, S(XY) denote the line segment determined by points X and Y, and P(Z,XY) denote the line through point Z and parallel to L(XY). L(YX) = L(XY), R(YX) != R(XY), S(YX) = S(XY) S(XY) = R(XY) ^ R(YX) CONSTRUCTION SCHEMA: CIR(XYZ,r) : For fixed points Y and Z and fixed length r - construct point X such that Y lies on S(XZ) and |XY| = r. CONSTRUCTION: If ( the point lies on L(XX') for some triangle vertex X ) { L(XX') is the desired line. } else { Let P be the given point and G the centroid of the triangle. Label the triangle ABC such that R(GP) intersects S(CB'). Construct point R such that R = P(P,AB) ^ L(AC). Construct point S such that S = P(B',BR) ^ L(AB). If ( P lies on the triangle ) { L(PS) is the desired line. } else { Construct point T as the midpoint of S(AS). CIR(QRP,|PR|). CIR(DAT,|PQ|). Construct a semicircle with diameter S(DT) on the opposite side of S(DT) from vertex C. Construct a line through vertex A, perpendicular to S(DT), intersecting semicircle DT at point E. If ( P is outside the triangle ) { CIR(FTA,|TE|). L(PF) is the desired line. } else { Construct point H such that |EH| = |AT| and H lies on S(AT). CIR(KTH,|AH|). L(PK) is the desired line. } } }
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